They produce the chassis for the diyaudio store but if you are in Europe best to order direct from them. However, good idea to use the specs provided by the diyaudio store when ordering because you will then get the heatsinks drilled and tapped for the mosfets on the power board and the back plate ready for speaker posts and mains sockets etc. Also the base plate in the amp chassis that I got doesn't align with the holes in the pcb modules but they now have one that addresses this issue. None of these things is that important it just means you spend a bit longer away from your nearest and dearest. Can be good can be bad!

"At the moment I’m driving a pair of Lowther DX55’s with some passive baffle-step correction (6 dB loss there) and an F3 amp with only 12.5 dB voltage gain. The preamp is fed by an Xono phono stage with a low output cartridge (Grado Statement).
The sound is extremely neutral without being clinical - just about what you were looking for when you were thinking about a passive preamp. A teensy bit of second harmonic and no noise at all.
There’s just enough gain. If you were using any other power amp, you’d get 8 to 18 dB more gain, and would be able to break your lease or the speaker, or both."

The 8 to 18 db more gain is what I'm curious about. Anyone want to take a guess, or provide a formula that can predict how that would translate to the BA-3 when compared to the F3 Mr. Pass was using ?

I think what he is saying is that 12.5db is a very low voltage gain and a typical amp will have 20 - 30db of voltage gain.

The B1 is a buffer so what comes in is what comes out (voltage wise) so with a low gain amp (perhaps designed to work with a preamp with gain) you might not get enough volume to shake the rafters.

As the BA3 has 30db of gain by default it should be absolutely fine with a B1. As I posted earlier I'm looking at dropping it to 20db which I think should be adequate and I will effectively be using a B1 with it. I say effectively because there will also be active filters in the circuit.

Tony.

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Any intelligence I may appear to have is purely artificial!Some of my photos

One could read that paragraph and get the impression there could be a multiplier effect dependent on amp selection/combination - at least I did, which didn't sound like a buffer. Thanks for clearing that up.